Electric furnace



1 WI SSES:

O. A.- COLBY.

ELECTRIC FURNACE.

APPLICATION FILED MAR. 31. 1920. 1,412,531 1, Patented Apr. .11, 1922.

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INVENTOR I Ora A 60/9. 1 BY v ATTORNEY srarss PATENT orice.

033.55. A. COLBY, l3 IRW IN, FENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC 85 MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC FURNACE.

Specification of Letters Patent. Patented Apr; 11, 1922.

Application filed March 31, 1920. Serial No. 370,074.

T all whom it m (1 7 concern.

lie it known that l, ORA A. Count, 3 citizen of the United States. and a resident of Irwin, in the county oflVestmoreland and State of Pennsylvania, have invented a new and useful Improvement" in Electric Furnaces, of which the following is a specification.

lily invention relates to electric furnaces and particularly to furnaces of the electri cal-resistance type, and it has for one of its objects to provide a high-temperature resistance furnace suitable for melting alloys which shall utilize solid blocks of refractory conducting material as a resistor.

Another object is to provide improved means for conducting the current to and from the resistor which means shall permit of operating the'furnace continuously for relatively long periods of time.

In the single sheet-of drawings, Figure 1 is a horizontal cross-sectional view of a furnace embodying my invention, taken along the line 1-1 of Fig. 2, and Fig. 2 is a crosssectional view, in elevation, taken on the line ll-ll of Fig. 1.

The supporting structure of the furnace comprises an exterior metal frame or casing 1. inside of which is placed a shell 2 of heatinsulatingbrick and an inner shell '3 of fire brick. The inner walls of the shell 3 are so spaced apart as to form a chamber 1 substantially rectangular in outline. In this chamber are placed a plurality of parallelextending resistor blocks 5 which are so spaced apart that a crucible 6 may be placed therehetwcen, the floor of the chamber 4 being raised in the central part of the cham' her to such height as may be required to bring the top of the crucible 6 substantially level with, or just beneath, the top of the furnace itself.

in order to provide means for holding the resistor blocks 5 in their proper operative positions in the chamber i, a body 5, composed of a. mixture of crucible clay and graphite, is so placed between the outer end and a portion of the outside of each resistor block, near the end thereof, and the inner wall of the chamber wall 4i as to space the resistor blocks slightly from the side walls and to form an air pocket Tbetween the outside of the resistor bloehs and the inner wall of the chamber 4:. 'lhis pocket of air operates to prevent the heat from being conducted to the walls of the chamber 4 and then on out to the outer surface ofthe furnace which would reduce the heat eiliciency of the furnace.

A plurality of substantially V-shaped carborundum blocks 8 is placed between the parallelextending resistor blocks 5, the shape of these blocks being so selected that a relatively small chamber 9 is formed in which the crucible 6 may be placed. \Vhile I have shown the chamber 9 to be substantially octagonal in. outline, this is not essential and the main consideration is to obtain an outline of the chamber which shall he as nearly circular as it is possible to obtain with carhorundum blocks.

The blocks 8 co-operate with the inner wall of the well 3, on two sides thereof, to form wells or hoppers 10 into which the ends of. the resistor blocks extend. The wells 10 extend downwardly below the lower end of the crucible, and a terminal electrode 12 extends into each of these wells and may eX-i tend to a point outside of the furnace itself. Metal terminal plates 13 are suitably connected to the terminal electrodes which may consist of solid carbonaceous material, and the electric supply-circuit conductors (not shown) may be suitably connected to the metal terminal plates. A mass of electricalconduoting granular material is placed in.

each of the wells 10 and is thoroughly packed or tamped into place so that it will have close operative contact with both the upper surface of the te'rminal'elect-rode '12 in the well itself and with the side of the resistor blocks 5 and 8 and thus serve to conduct the current into and out of the resistor blocks It has been found impracticable to maintain operative engagement between solid carbonaceous blocks during the operation of a furnace of this type on account of the slow oxidation of the surface of such material which results in arcing therebetween. By the use of the above-described means, I provide a low-resistance path from the terminal electrode to the resistor the material of which may be easily retamped when a certain am unt of oxidation has taken place and in which it is a relatively easy matter to replace the entire mass of granular material nhenever this becomes necessary.

A cover member (not shown) may be provided for the furnace to reduce the heat losses therefrom and this cover member may be suitably hinged to the metal shell 1 or may be lifted off entirely by suitable means whenever necessary.

It will be noted that I provide a resistor which may be placed relatively close to a crucible and with which such a furnace may be operated for IQlQtlXClY lone; periods of time Without requiring attention. It may also be noted that an improved method of conducting current to and from the resistor locks is employed which permits of easy renewal of the conducting material should this material become oxidized to any considerable extent.

While I have shown a"specilic embodiment of my invention, various cl'ianges may be made therein without departing from the spirit and scope of my invention, and I desire that only such limitations shall be placedthcreon are imposed by the prior art or are specifically set forth in the appended claims.

claim as my invention:

1. In an electric furnace, the combination With a refractory casing, of a crucible in said casing, a resistor adjacent said crucible comprising solid blocks of refractory electrical-conducting material, hoppers in said casing opposite the ends of said resistor, terminal electrodes in said hoppers, a mass of electrical-conducting granular material interposed between said electrodes and said resistor, and means for holding said resistor blocks in their operative positions in said casing.

2. In an electric furnace,

the combination with a refractory casing, of a container in said casing, two parallel-extending heating, elements adjacent to said container, said heating elements comprising solid blocks of refractory electrical-conducting material, hoppers opposite the ends of said blocks, solid carbonaceous terminal electrodes in said hoppers, a mass of clectrical-conducting granular material interposed between said electrodes and said resistor blocks, and blocks of solid refractory material between said parallel-extending resistor blocks and adjacent to said hoppers.

3. .ln an electric furnace, the combination with a refractory casing, of a container in said casing, sets of parallel-extentling rcsistor blocks of refractory material on each side of said container, hoppers opposite the ends of said sets of resistor blocks, solid carbonaceous terminal electrodes in said hoppers, masses of granular BlPCtIlClll-(:()l1- ducting material interposed between said electrodes and said resistor blocks, said masses being of greater cross-section than the electrodes to prevent overheating of said electrodes, blocks of solid refractory material adjarcnt said hoppers and between said parallel-extending resistor blocks, and jacketing means outside of said resistor blocks to reduce the amount of heat conducted away from resistor blocks.

in testimony whereof, l have hereunto subscribed my name this 26th day of March, 1920.

ORA A. COLBY. 

